Balancing machine



Aug. 28, 1945. s. BOUSKY 2,383,588

BALANCING MACHINE Filed Nov. 20, 1942 e Sheets-sheaf 1 v I INVENTOR. 3 29999?? /6'0Mua flaws/(Y I BY ATTOENE).

Aug. 28, 1945, s. BOUSKY 2,383,588

BA ANCING MACHINE Filed Nov. 20, 1942 6 sheets-sheet 2 INVENTORQ SaMl/aBoas/(V BY ATTOENEK Aug. 28, 1945. s. BOUSKY BALANCING MACHINE 6Sheets-Sheet 3 Filed Nov. 20, 1942 -INVENTOR. 679mm .Bausxr ATTOf/VEKAug. 28, 1945. s. BOUSKY I BALANCING MACHINE Filed Nov. 20, 1942 6Sheets-Sheet 4 INVENTOR. \SHMUEL .BOl/JWY.

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Aug.28, 1945. s. BOUSKY 2,383,588

BALANCING MACHINE Filed Nov. 20, 1942 6 Sheets-Sheet 5 INPUT TRANS-RANGE BAND PASS FILTER duh MSv'u aaoasoaozus (DOOOOO INPUT TRANS- BANDPASS FILTER RANGE TCH FLASH FIER TIME WAVE GENERATOR FROM H A IR SUPPLYSAMUEL .BOUSKY.

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Aug. 28, 1945. s, BOUSKY 2,383,588

BALANCING MACHINE Filed' Nov. 20, 1942 6 Shets-Sheet 6 IIIIIIHI HHIHIHIIIIIIHII IN VEN TOR. Swan Boas/0f ATTOENL'Y.

Patented Augl 28, 1945 BALANCING MACHINE I Samuel Bousky, ShakerHeights, Ohio, assignor i Jack & Heintz poration of Ohio Inc. Bedford,Ohio, a cor- Application November 20, 1942, Serial No. 466,265

ii Claims.

This invention relates-in general to balancing machines, or in otherwords to improvements in devices for determining and indicating theamount and location of dynamic unbalance or state of dynamic balance ofhigh speed'rotating Figure 4 is an enlarged view of the rotor suspensionassembly showing in dotted lines the slidmasses such as gyro rotors,armatures and the like.

One of the primary objects of the invention is to provide a testingdevice that will properly and accurately simulate the conditions ofactual operation that will permit unbalance determinations of the rotorthat would actually occur under actual operation thereof.

A further object of the invention is to provide in such a testingdevice, a rotor bearing suspension and electrical pick-up assemblywhereby the rotor bearings will lie in parallel planes and will beresiliently suspended so as to be substantially free to move in alldirections within a plane at right angles to that of the rotor so that,under the influence of unbalance forces, motion of the bearings iseffected to drive the pick-up units to generate electrical voltageswhich are proporv tional to the movements of the bearings.

- A further object of the invention is to provide in such a testingdevice improved electronic circuits to properly amplify the minutepick-up voltages; select the proper components and mix them in theproper phase and magnitude relationships.

A further object of the invention is to provide in such a testing devicemeans whereby the position of unbalance is indicated separately on bothsides of the rotor by a stroboscopic lamp which flashes directlythereon. l

A further object of this invention is to provide an electrical pick-upassembly and associated electronic amplifier and filter circuits of suchextreme-sensitivity as to permit unbalance determinations of a degreehitherto unattainable.

With the foregoing and other objects in view the invention resides inthe combination of parts and in the details of construction herein-afterset forth in the following specification and appended claims, certainembodiments thereof being illustrated in the accompanying drawings, inwhich:

Figure 1 is a view in front elevation of the device showing the rotorsuspension assembly and the cabinet for the electrical and pneumaticoperating system;

Figure 2 is a view in side elevation of the device shown in Figure 1;

Figure 3 is a view in section taken along line 33 of Figure 1 partlybroken away showing the rotor suspension assembly in top plan;

able support and latching device for the movable suspension member;

Figure 5 is a view in section taken along line 5-6 of Figure 4 showingthe rotor suspension device and the slidable support and latching devicefor the movable suspension member; I

Figure 6 is a view in section taken along line 6-6 of Figure 4 showingin section one of the suspension wires for the rotor bearing disc and hedamping means for the suspension wire;

Figure 7 is an enlarged view in section taken along line 1-"! of Figure4 showing in side elevation one of the rotor bearing discs and itssuspension as well as a pick-up unit and rotor driving air jet; 7

Figure 8 is a view in end elevation of the stationary support for one ofthe rotor bearing plates;

Figure 9 is a view in section taken along line 9-9 of Figure 4 showingthe slidable support for the other bearing plate and the means forlocking the same in place; 8

Figure 10 is an enlarged view in vertical section taken through one ofthe pick-up assemblies;

Figure 11 is a'view in section taken along line ii-li of Figure lo;

Figure 12 is a view in vertical section taken through a modified form ofbearing plate and its support;

Figure 13 is a schematic illustration including. the rotor and thepick-ups and the electrical and pneumatic system of the testing device;

- Figure 14 is a. schematic illustration of the gyro wheel rim andbuckets showing the numeralindicia on one side of the rim and the lineson the same for indicating purposes;

Figure 15 is a view in perspective of the gyro rotor with indicia on itsrim and with lightening drill holes made in the side wall afterthebalancing testing operation;

' Figure 16 is a partial view of the suspended rotor similar to thatshown in Figure 4 with theoretical rotor unbalance displacements forpurposes of explanation of forces involved in the operation of thedevice;

Figure 17 is a diagram of the voltages induced in one pick-up due to theforces in one bearing;

Figure 18 is a diagram of the voltages induced in the other Dick-up dueto the forces in the other bearing; and

Figure 19 is a diagram representing the mixing of the voltages inducedin the two electrical pickups.

anchors the wire in cylinder Referring more particularly to thedrawings, the testing device generally comprises a cabinet I for housingthe electrical and pneumatic equipment and a table 2 connected theretoby supports 3 for supporting the gyro rotor suspension, the dynamicpick-ups, stroboscopic lamp, electric switches and indicating meter.

The gyro rotor 4 under test is supported for horizontal rotation withitspivots 5 and .6 engaging ball bearing assemblies 1 and 8 carried byplates 9 and HI that are resiliently suspended and adjustable to lie inparallel vertical planes. These plates are suspended so as to be free tomove in all directions within a plane at right angles to the axis ofrotation of the gyro rotor 4 about its pivots 5 and 6. In order toaccomplish this there is provided a fixed preferably non-magneticsupport I01 and a slidably adjustable preferably non-magnetic supportI08. To each of these supports are secured preferably threeequidistantly spaced assemblies such as shown in detail in Figure 6which consists of a fluid filled cylinder II with a small breather |2.

Through the cylinder extends a fine strong wire |3 screw threaded at oneend to receive an adjusting nut l4. The other end of the cylinder issealed by a flexible diaphragm l5 held in place by a knurled cap |6through which the wire extends to engage an aperture in the bearingplate In near its periphery and is held in place in bearing plate H) bya screw IT. A screw H The wire l3 carries a suitable number of beads l8which preferably have roughened surfaces. Although the wires are tautthe effect of this arrangement is that while it is suflicientlyresilient to permit substantially free movement of bearing plate H) suchmovements are damped without materially affecting the natural period ofsuspension.

As a means of providing further flexibility of suspension the bearingplate of Figures 1, 3, 4 and 5 may be modified, as shown in Figure 12,to include the same hub portion but a diaphragm portion 9 sufficientlythin to afford a suitable degree of flexibility.

In order to safeguard against errors due to extraneous vibration thesuspension assembly is supported on table 2 in the following manner. Astationary base member 9 is secured to resilient shock absorbing webcarrying a metal plate 2| and secured to the table 2 by bolts 22 forresilient suspension. To this base is secured an end member 23 providedwith arcuate slots such as 24 with adjustment studs 25 to permit limitedrotational adjustment or support ||l1 andconsequently the bearing plate9. The purpose for locking this slide during the rotor testing operationin such a manner as not to distunb the thrust load. This is accomplishedby securing a plate 33 by bolts 34 to base I3. One end of tension spring32 is secured by a pin 35 to plate 33. The other end of spring 32 issecured by a pin 36 to the slide 3| which in its sliding movemerit moveson ball bearings 31 between the slide and the base. With the rotor inposition with its pivot 5 inengagement with its bearing 1, the slide isallowed to be moved home under the influence of spring 32 until pivot 6is engaged by its bearing 8. As a means for locking the slide in suchadjusted position there is provided a slide cage comprising walls 38 and39, a top plate. 40, and a retainer plate 4| with holes thereinsufllciently large to allow a portion of the balls 42 to protrudedownwardly therethrough, as shown in Figure 5. Intermediate the balls 42and the top plate 40 is a floating plate 43 downwardly urged resilientlyby a leaf spring 44. Thus when spring 32 has urged the support I08 andthe bearing plate I0 home a handle 45 is manually turned which throughits connection with a screw bolt -46 brings about a tightening of theadjustable relationship between the top plate 40 and the wall 38 throughwhich the bolt passes. This, through the flexibility of top plate 40 inthe portion shown at 40a, resiliently locks the slide 3| in abutmentwith the cage 3| as the balls 42 recede into the cage.

The electrical pick-up units 28 and 29 are arranged to be driven by eachof the bearing support plates 9 and Ill, respectively, by reason of theconnecting wires 26 and 21. Each of these pick-up units is identical inconstruction and purpose and one of these, which for the purpose ofreference will be called unit 28, is shown in detail in Figures 10 and11, and in which the housing is indicated at 28. In this housing isreleasably inserted a permanent magnet 41 which is held in place by aspring clip 48. Resting on top of the magnet is a magnetizable block 49inserted in the guideway 50 of the casing. Inside of the block is around magnetizable core 5| that may be adjustable longitudinally andlocked in adjusted position by a set screw 52. The metal plate 53abutting the magnet 41 is provided with a gap opening 54 to receive thereduced end 55 of the core 5| and the coil bobbin 56 mounted forhorizontal movement within the gap 54 and about the core 55. This mountconsists of a bracket 51 secured to the plate 53 to resiliently supporta bobbin arm 58 which has a chuck 58a to receive wire 26 and a set screw59 to secure the wire in place. Vibrations of the rotor as transmittedfrom bearing plate 9 through wire 26 will cause a reciprocation of arm58 in 1 its bearing bracket 51. This motion is restricted tosubstantially a reciprocatory one by means of two opposed leaf springs60 and 6| secured to the bearing bracket 51 and secured at spaced pointsto the bobbin arm 58. The insulated cable 62 leading from the housing 28into the cabinet and the electric system encloses two spaced insulatedwires 63 and 64. As viewed in Figure 10 wire 63 connects to one end ofpick-up coil wound on bobbin 56. The other end of this coil connects toneutralizing coil 65a. Wire 64 then connects to the other end ofneutralizing coil 65a electrically. Coil 65a and the pick-up coil onbobbin 56 are connected so as to be bucking for cancelling out theeffects of any voltages induced by the action of stray varying magneticfields.

The resultant construction is the formation of two bucking coils inseries wherein the coil about the insulator 65 plays no direct part asto generation of electromotive force due to the motion plate 53, beingin contact with permanent magair jet.

net 41, is magnetized and the reciprocatory movement of bobbin 58 andits coil break through lines of force so as to generate electricalvoltages in response to and proportional to the minute motions of therotor bearings due to their state of unbalance during rotation.

The gyro rotor is preferably driven pneumatically by an air Jet 88expelling air under pressure against the rotor buckets 81. Two valvesystems are incorporated in the instrument, one operated by foot forbringing the rotor up to speed rapidly and another operated by handproviding a needle valve adjustment for maintaining the desired speed ofgyro rotor rotation during test. As shown schematically in Figure 13,air

lationship with that which occurs on the right side, The voltagesgenerated in the two pick-ups dueto the left unbalance mass will thenproduce a masking effect on the location of the right mass.

For purposes of graphic illustration, reference will be had to Figures16 to 19, inclusive, and in connection with Figure 16, it will beassumed that there exists an unbalance mass X on face F1 of rotor landan unbalance mass W on rotor face F8. It should be borne in mind that inthe present invention the resilient rotor suspension means and the speedof rotation of under pressure is drawn in through pipe 88 from asuitable source of airsupply. The air is then drawn through an airfilter 69 and air regulator 10 provided with an air gauge II and throughpipe 88 past a hand shut-off valve 12 and adjustable needle valve 13 tothe air Jet 66. A by-pass for the air is provided through junction pipe14 leading through a foot valve 15 and a pipe 18 by-passing the handvalves and Joining pipe 88 at 11. In operation the foot valve isoperated to direct the air from pipe 88 at Junction 18 through pipes 14and 16 at gauge pressure to the- When the rotor has gained the approxi-'mate desired speed the foot valve is released and shut-oil valve 12 andneedle valve 13 adjusted to meter and maintain the necessary pressureair flow to obtain the desired speed of rotor rotation.

As stated before, the minute pick-up voltages generated in the pick-upunits must be amplified and their proper components selected andmixed inproper phase and magnitude relationships. Figure 13 also showsdiagrammatically the ar- 'rangement and purpose of theelectroniccircuits employed in the balancing machine. Voltages aregenerated in the two identical pick-up units 28 and 28 which areproportional to the unbalance movements of the right and left sides ofthe rotor. These electrical voltages are very minute and in magnitudethey may be measured in the Y order of a few millionths of a volt. Thesevolt- 18 serves mainly as a voltage step-up device from the lowimpedance pick-up unit to the higher impedance range selecting switch88. The range selecting switches are mechanically interconnected so thatboth electrical channels are simultaneously switched when any one of theswitch I ment of the rotor under test and rejects all other extraneousvoltages such as those produced by ball bearing noises and othervibrations. In addition this band pass filter is preferably one that haslow phase shift characteristics in the pass band. After suchamplification and filtering the two voltages are mixed in the properamplitude and phase so that the unbalance may be referred to one side ofthe rotor at a time. The theory and practice involved in this procedureis as follows:

Consider an unbalance mass occurring only on the right side of therotor. Voltages will be generated in both pick-ups 28 and 29 due to thisunbalance mass when the rotor is rotated. Consider in addition anotherunbalance mass on the left side of the rotor but in a different phaserethe rotor are so chosen that the latter is considerably greater thanthe naturalperiod of suspension. Such being the case, the presence ofweight X on face F1 on the left side of the rotor will produce a greatervibration on bearing 8 at the right side than on bearing 7 on the leftside.

Referring to Figures 17, 18 and 19, let W! indicate the instantaneousunbalance displacement of bearing I due only to the unbalance mass W onrotor face F8. Similarly, let X8 indicate an .instantaneous unbalancedisplacement at bearing 8 due to mass X on face F1. The resultantdisplacement R1 at bearing 1 will be the total effect of X1 and W! ofmasses X and W. Similarly, the resultant displacement at bearing 8 isvectorially developed as R8 as being the total of X8 and W8.

Disregard for the time being the phase differ- 1 ence between thedisplacement and its electromagnetically generated voltage and considerR1 and R8 to also represent the voltages in pick-ups 28 and 29.Electrically speaking, if as shown in Figure 19 a small portion of R8,namely R'8,

be added to R1 at 180 phase reversal of R8 and of such magnitude thatcomponent X8 is exactly equal to X! but 180- different in phase, thenthe resultant of this addition will be WI minus W8, a quantity thatdepends only upon mass W and which is representative of it both inmagnitude and phase. The proper ratio X8/X'8 is a function only of thelinear dimensions of the rotor and the bearing spacings and is thereforea constant for a given type of rotor.

\ Thus it is seen that by mixing the voltages in the two channels withproper regard to magnitude and phase, a resultant voltage is attainedwhich is representative of unbalance on only one side of the rotor. Byelectrically reversing this mixing method relative to the two channels,the unbalance on the other side of the rotor can be indicated.

In this manner there is imulated the condition of using two pivotssimultaneously without the need of the mechanical structure of two fixedpivots. This is obtained by operation above resonance wherein-theunbalance mass on one side must be 180 out of phase with thedisplacement on that side. Theparticular suspension provides thenecessary axial rigidity as well as the necessary freedom of movement inany direction within the plane at right angles to the axis of suspensionof the rotor to accomplish the above described phenomenon.

Such a voltage is then fed to the selective amplifler 88 which furtherrejects extraneous and interfering voltages. At this point a meter 88 isarranged to indicate the magnitude of the unbalance force directly-inmicro-ounce-inches, or in terms of millionths of an ounce-inch. Thevoltage from the selective amplifier 88 is used to locate the positionof the unbalancemass. By

means of a foot-operated switch I09 the output voltage from amplifier 85is fed into flash amplifler 92 where it is amplified and its wave shapeis changed so as to present an extremely sharp wave front for flashingthe stroboscopic lamp 93. In this manner the stroboscopic lamp isflashed momentarily and once for each revolution of the rotor. Theflashlamp is on for such a short interval that it appears to stop therotation of the rotor and indicates by this means the position at whichthe unbalance mass occurs. This rotation can be readily identified bythe indicia appearing on the wheel as illustrated in Figures 14 and 15.When the foot switch I09 is operated to its other position a voltagefrom the time wave generator H is fed into the flash amplifier 92 andthus operates the stroboscopic flash lamp 93.

The speed of the rotor when rotating is determined by this means sincethe indicia 40 on the rotor will appear to be stationary or rotateslowly when the rotor is rotated at substantially the same rate as thevoltage generated by the generator H0.

As previously explained, in the operation of the testing device, therotor pivots are thoroughly cleaned, the table slide 3| is held with onehand while rotor 4, with its printed numbers on one side 4a, is placedbetween the bearings I and 8 with the other and the slide is releasedleaving spring 32 free to move the same home, after which it is lockedin place by lever 45. The hand operated valve 13 is turned on afterwhich the foot operated valve I is depressed to by-pass the air flow forquickly bringing the rotor up to the desired speed of rotation. The footoperated switch I09 is then operated to cause the stroboscopic flashlamp 93 to flash at the rate of 12,000 times per minute. In about fiveto ten seconds the rotor attains a speed of rotation of 12,000revolutions per minute. At this point the foot operated air valve 15 isreleased and fine control of rotor speed is obtained by operation of thehand operated needle valve 13. With the rotor at such speed themagnitude of the unbalance ofthe rotor is read directly on the meter 99,with the aid of a six push button range selecting switch 8| arrangedconveniently at the front of table 2. Readings may be taken either inmicro-ounceinch units or by means of some suitable convenient series ofnumbers on the meter dial 89.

With the rotor at speed an indication of the position of unbalance ofthe rotor is obtained by releasing the foot switch 109 and observing thestroboscopic position of the rotor. The printed number on the rotor rimwhich is thus stroboscopically illuminated is the point of unbalance andthe point at which the rotor is to be drilled, to lessen the weight, toeffect a perfect balance. Such a drilled point is shown at 95 oppositethe printed number 94 on the rim to of the rotor, shown in perspectivein Figure 15.

where small electrical phase shifts occur and also several points where180 phase reversals occur. Actually there preferably is a phasecorrecting network that may be included as a part of a flash amplifier92 but preferably in the form of a phase network I I I separate from butin circuit with the flash amplifier. Correction for all of the abovementioned phase shifts may be taken care of in this one phase correctingnetwork having a. variable adjustment to serve as a calibrating means sothat the proper indicia on the rotor may be illuminated at the properpoint.

The method of operating the rotor at a speed greater than the naturalperiod of resilient support is an advantage in that it permits unbalancetesting at extremely high speeds while permitting sumcient resilience inthe support for appreciable amplitude of displacements to accomplishsensitivity. Morever, the displacements of the supports are directlyproportional only to the unbalance torque and inversely proportional tothe total mass of the rotor except as slightly affected by the dampingmeans provided on the resilient support whereas operation belowresonance would There are actually many phase changes in the balancingmachine that are taken into considera-, tion in the construction of themachine. The rotor suspension and the operation of the rotor are suchthat there is an 180 phase difference between the position of theunbalance mass and the displacement in two electrical planes. There isalso a small mechanical phase shift due to the damping on the resilientsupport. Since the voltage generated in the pick-ups is by means of amoving coil, this voltage is proportional to velocity and thereforediffers in phase by 90 with the movement of the coil. There are severalplaces in the amplifiers and in the mixing circuit make the displacementdirectly proportional to the unbalance torque times the square of thespeed of rotation and inversely proportional to the spring constant. Italso provides an eifective dynamic gyrating system which gives theeffect of two pivots acting simultaneously.

In the right-and-left switch are two buttons marked L and R." If the "Lbutton was depressed during the above test the data applies to the leftside of the rotor. While maintaining rotorspeed the B button is thendepressed and magnitude and position readings of rotor unbalance aretaken for the right side.

For -balancing, the table air valve I3 is shut off, the rotor stoppedand removed from the test stand and placed on alsuitable drill press.The rotor is drilled on each side at the position indicated and to adepth corresponding to the amount of unbalance. After drilling, theabove procedure is repeated again or as many times as bearing assemblieseach including a plate and anti-friction bearings carried therein forreceiv-' ing and supporting each end of the axle of the rotor, separatesupporting standards on either side of said rotor, separate cantileversuspension means for suspending each of said plates including aplurality of cantilever members disposed at right angles to said plateand connected at their inner ends to said plate and at their outer endsto said adjacent standard with radial clearance in the latter for themain body of the cantilever members for maintaining said bearingassemblies substantially parallel to each other so as to permit movementof said cantilever members in said standards and movement of eachbearing assembly independently of movement of the other cantilevermember and bearing assembly in any direction within the planes at rightangles to the axis of rotation of the rotor, separate means connected toeach of said bearing suspension means adapted to be driven thereby inplanes at right angles to the axis of the rotor in response to a stateof unbalance thereof for setting up electrical voltages in response tomovements of each of said bearing suspension plates and means foramplifying said voltages and for indicating the amount of unbalance ofsaid rotor and means controlled by said voltages for indicating thelocation of unbalance of the rotor.

2. In a testing device. for rotors, controllable means for rotating therotor to be tested, separate .bearing assemblies substantially parallelto each tilever members in said "units connected to each nected at otherand so as to permit movement of said canstandards and movement of eachbearing. assembly in any direction within the planes at right angles tothe axis of rotation of the rotor and independently of any movement ofthe other cantilever members and other bearing assembly, separateelectro-dynamic pick-up of said bearing suspension means and adapted tobe driven thereby in response to a state of unbalance of said rotor andset up electrical voltages in response to resulting movements of each ofsaid bearing suspension means, means for amplifying said voltages, ameter connected to said amplifying means for indicating the amount ofunbalance of said rotor, said rotor having indicia on its rim, means forindicating the angular position of unbalance of said rotor on said rotorincluding a stroboscopic lamp mounted adjacent the rim of said rotor andmeans responsive to the voltages set up in said pick-up units forflashing said lamp for instantaneously illuminating said indicia,

3. In a testing device for rotors, controllable means for a source offluid pressure adapted for rotating the rotor to be tested, separatebearing assemblies each including tion bearings carried therein forreceiving and supporting each end of the axle of sai rotor,

separate supporting standards on either side of said rotor, ity ofconcentrically arranged cylindrical members extending outwardly at rightangles to said standard, for suspending each of said plates including aplurality of wire-like cantilever members contheir inner ends to saidplate and extending with radial clearance in said cylindrical membersand fixedly connected to the outer ends thereof to be relatively tautfor maintaining said bearing assemblies parallel to each other so as topermit movement of said cantilever members in said standards andmovement of each hearing assembly in any direction within the planes atright angles to the axis of rotation of the rotor and independently ofany movement of the other cantilever members and other bearing assembly,sep arate electro-dynamic pick-up units connected to each of saidbearing suspension means and adapted to be driven thereby in angles tothe axis of the rotor responsive to a state of unbalance of said rotor,means for proportionately amplifying said voltages, a meter connected tosaid amplifying means for indicating the amount of unbalance of saidrotor, said rotor having indicia on its rim, means for indicating theangular position of unbalance of said rotor on said rotor including astroboscopic lamp mounted adjacent the rim of said rotor and controlmeans responsive to the a plate and anti-fricsaid standards eachcarrying a pluralseparate cantilever suspension means tending outwardlyat ard, separate cantilever suspension means for voltages set up in saidpick-up unitsfor flashing said lamp for instantaneously illuminatingsaidindicia.

4. In a testing device for rotors, controllable means for a source offluid pressure adapted for rotating the rotor to be tested, separatebearing assemblies each including a plate and anti-friction bearingscarried therein for receiving and supporting each end of the axle ofsaid rotor, separate supporting standards on either side of said rotor,said standards each carrying a plurality of concentrically arrangedcylindrical members exright angles to said standsuspending each of saidplates including aplurality of wire-like cantilever members connected attheir inner ends to said plate and extending with radial clearance insaid cylindrical members and fixedly connected to the outer ends thereofto be relatively taut for maintaining said bearing assemblies parallelto each other so as to permit movement of said cantilever members insaid standards and movement of each bearing assembly in any directionwithin the planes at right angles to the axis of rotation of the rotorand independently of any movement of the other cantilever members andother bearing assembly, means for damping the radial movements of saidcantilever members in said cylindricalmembers and consequently theradial movements of said bearing assembly supporting plates, separateelectrodynamic pick-up units connected to each of said bearingsuspension means and adapted to be driven thereby in angles tov the axisof the rotor responsive to a state of unbalance of said rotor, means forproportionately amplifying said voltages, a meter connected to saidamplifying means for indicating the angular position of unbalance.

of said rotor on said rotor including a stroboscopic lamp mountedadjacent the rim of said rotor and control means responsive to thevoltages set up in said pick-up units for flashing said lamp forinstantaneously illuminating said indicia.

5. In a testing device for rotors, controllable means for rotating therotor to be tested, separate bearing assemblies each including a plateand anti-friction bearings carried therein for receiving and supportingeach end of the axle of said rotor, separate supporting standards oneither side of said rotor, said standards each carrying a plurality ofconcentrically arranged cylindrical members extending outwardly at rightangles to said standard, separate cantilever suspension means forsuspending each of said plates including a plurality of wire-likecantilever members connected at their inner ends to said plate andextending with radial clearance in said cylindrie .cal members andfixedly connected to the outer ends thereof to be relatively taut formaintaining said bearing assemblies parallel to each other so as topermit movement of said cantilever members in said standards andmovement of each cantilever members to be immersed in said fluid fordamping the radial movements of said cantilever members in saidcylindrical members and consequently the radial movements of saidbearing assembly plates for supporting said rotor, separateelectro-dynamic pick-up units connected to each of said bearingsuspension means and rim, means for indicating the angular position ofunbalance of said rotor on said rotor including a stroboscopic lampmounted adjacent the rim of said rotor and control means responsive tothe voltages set up in said pick-up units for flashing said lamp forinstantaneously illuminating said indicia.

6. In a testing device for rotors, controllable means for rotating therotor to be tested, separate bearing assemblies each including a plateand anti-friction bearings carried therein for receiving and supportingeach end of the axle of said rotor, separate supporting standards oneither side of said rotor, said standards each carrying a plurality ofconcentrically arranged cylindrical members extending outwardly. atright angles to said standard, separate cantilever suspension means forsuspending each of said plates including a plurality of wire-likecantilever members connected at their inner ends to said plate andextending with radial clearance in said cylindrical members and fixedlyconnected to the outer ends thereof to be relatively taut formaintaining said bearing assemblies parallel to each other so as topermit movement of said cantilever members in said standards andmovement of each bearing assembly in any direction within the planes atright'angles to the axis of rotation of the rotor and independently orany movement of the other cantilever members and other bearing assembly,each of said cylindrical members having its inner end provided with aflexible diaphragm through which one of said cantilever members extends,each of said cylindrical members being filled with fluid and each ofsaid cantilever members having beads immersed in said fluid for dampingthe radial movements of said cantilever members and consequently theradial movements of said bearing assembly plates for supporting saidrotor, separate electro-dynamic pick-up units connected to each of saidbearing suspension means and adapted to be driven thereby in angles tothe axis of the rotor responsive to a state of unbalance of said rotor,means' I amplifying said voltages, at

for proportionately meter connected to said amplifying means forindicating the amount of unbalance of said rotor, said rotor havingindicia on its rim, means for indicating the angular position ofunbalance of said rotor on said rotor including a stroboscopic lampmounted adjacent the rim of said rotor and control means responsive tothe voltages set up in said pick-up units for flashing said lamp forinstantaneously illuminating said indicia.

SAMUEL BOUSKY.

